Sao Paulo have announced the signing of Brazil international midfielder Souza on a permanent deal from local rivals Gremio.
Souza has made 27 first-team appearances since joining Sao Paulo on loan in January, playing a key role in the club's bid for a first Brazilian Serie A title since 2008, reported Xinhua.
"Since my first day at the club I have said that I feel good here," the 25-year-old told Sao Paulo's official website.
"Luckily I have been able to adapt quickly and make some great friends. (Coach) Muricy (Ramalho) has also helped me a lot in this time. I can only express my gratitude for everything that Sao Paulo has done for me. I hope to stay at the club for a long time."
The former Porto and Brazil under-20 player was rewarded for his consistent form by being called up by national coach Dunga earlier this month.
He made his international debut in Brazil's 4-0 victory over Japan in Singapore Oct 14.